Add license headers

[odow]

x-ref jump-dev/MathOptInterface.jl#1813

[codecov]

Codecov Report

Merging #114 (be4ba73) into master (04579d7) will increase coverage by 0.28%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #114      +/-   ##
==========================================
+ Coverage   82.96%   83.24%   +0.28%     
==========================================
  Files           3        3              
  Lines        1303     1313      +10     
==========================================
+ Hits         1081     1093      +12     
+ Misses        222      220       -2     

Impacted Files	Coverage Δ
src/HiGHS.jl	100.00% <ø> (ø)
src/MOI_wrapper.jl	93.12% <ø> (+0.06%)	⬆️
src/gen/libhighs.jl	37.60% <ø> (+0.85%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 04579d7...be4ba73. Read the comment docs.